Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Mechanical defibration in the presence of heated gas or gas...
Patent
1983-12-23
1986-08-19
Alvo, Steve
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Mechanical defibration in the presence of heated gas or gas...
162 26, 162 55, 209 11, 209144, D21B 112, D21B 114, D21D 130, D21D 524
Patent
active
046067892
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is concerned with a method of manufacturing cellulose pulp from ligno-cellulose material wherein the material is ground in a mill which is subjected to internal steam pressure. The invention is further concerned with means for the implementation of the method.
In such manufacture of cellulose pulp, especially for paper making, it is necessary in order for the pulp to be used efficiently that said pulp consist of a uniform fibre fraction without oversize non-comminuted (non-defibrated) knots or bundles of fibres. In conventional pulp manufacture this is achieved by slurrying the manufactured pulp with water, whereafter it is caused to pass in the form of a relatively thin suspension through a variety of fibre sorting means such as screens equipped with perforated or slotted plates for the removal of shives, or so-called hydrocyclones wherein the stock is cleaned of shives and insufficiently comminuted (defibrated) bundles of fibres by centrifugal action.
All these so-called water-dependent systems suffer from the drawback of requiring large quantities of water, in the order of 1:300 to 1:100, which water must be removed in subsequent treatment before the pulp is transported to the point of use, baled, etc. The suspension of the pulp in water and the transportation of the large volumes of liquid to screens and, hydrocyclones takes a great deal of energy, and moreover, the oversize bundles of fibres or shives removed in the screens and hydrocyclones must be dewatered again to a concentration of approximately 1:2 to 1:4 for efficient further treatment thereof.
SUMMARY OF THE INVENTION
The main object of the invention is to provide a method of the above-mentioned type whereby the pulp as manufactured can be cleaned and the shives or bundles of fibres removed in the cleaning process can be subjected to further treatment, without the addition of substantial quantities of water which must subsequently be removed by various dewatering methods. A further object of the invention is to provide such a method, economical of energy and water, which can be implemented in combination with the mechanical separation of lignocellulose material at temperatures in excess of 100.degree. C. and/or at pressures exceeding normal atmospheric pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more particularly described hereafter with reference to an embodiment, illustrated in the accompanying drawings, of a plant for the implementation of the method.
FIG. 1 is a schematic diagram of a plant implementing the method.
FIG. 2 is a section through a type of mechanical separator that can be used in the plant of FIG. 1.
FIG. 3 is a section through another embodiment of mechanical separator.
FIG. 4 is a longitudinal section through yet another type of separator.
DETAILED DESCRIPTION OF THE INVENTION
In the plant illustrated in FIG. 1, the number 10 indicates a feed hopper for a lignocellulose fibre material, such as wood chips. From the hopper 10 the material is fed by a screw 12 to a pre-heater 14 and from there by a screw 16 to a first defibrator 18, such as a disc defibrator, wherein the lignocellulose material, such as wood chips, is comminuted to single fibres or bundles of fibres. In this treatment, which may or may not be preceded by chemical treatment and/or heating in the pre-heater 14, most of the energy supplied to the material in the defibrator 18 is converted into heat. The natural moisture present in the material and/or water added to prevent overheating of the fibre material during defibration in the defibrator 18 is thereby converted into steam.
The steam thus generated, together with steam, compressed air, or other gases added during or after the defibration process in the defibrator 18, is now used according to the invention for the very effective removal of large, unwanted bundles of fibres or shives without the addition of water. This separation is effected by using the gas or steam so generated to carry the fibre material at high velocity via a p
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Alvo Steve
Munson Eric Y.
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